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A miscarriage — known in medical jargon as a spontaneous abortion — is the unexpected end of a pregnancy before 20 weeks gestation. During a miscarriage, an embryo or fetus is spontaneously expulsed from the uterus but can’t yet live in the outside world. After 20 weeks, the loss of a fetus is called a stillbirth instead of a miscarriage.

Just because it often takes place early in a pregnancy doesn’t mean that miscarriage isn’t painful for expectant parents. What’s important to remember: Miscarriage is not your fault. And while many parents may not talk openly about having one, know that it happens much more often than you may realize. Read on to learn more about the causes and types along with risk factors.

What causes a miscarriage?

Miscarriages are not caused by moderate exercise, falls, sex, stress at work, fights with a spouse or morning sickness. Rather, a miscarriage is simply biology’s way of ending a pregnancy that’s not going right. The loss of the embryo or fetus and its expulsion from the uterus can be caused by many factors, ranging from genetic defects in the growing baby to immune reactions by the mother’s body. Often, the cause of a miscarriage is never pinpointed at all. And in nearly every case, there’s nothing the mother did wrong to cause the miscarriage or could have done differently to prevent it.

How common are miscarriages?

Much more common than you might think: Researchers have estimated that around one in six pregnancies end in miscarriage. But even that number may be an underestimation, since many miscarriages occur so early that they go unnoticed and are mistaken for a normal period instead. Even if you haven’t heard of anyone in your family or group of friends having a miscarriage, it’s likely someone in your close circle has gone through one. So if you experience a miscarriage, know that you’re certainly not alone.

Though you might have heard some people say it seems miscarriages are more common today than they were in the past, in fact they’ve always been common — it’s just that they may be detected more often now because of the advent of affordable, early at-home pregnancy testing.

When do most miscarriages occur?

Early miscarriages occur in the first trimester and account for 80 percent of all miscarriages. Of these, a large number occur in the first weeks of pregnancy, often before a woman even knows she’s pregnant. During the first trimester, a lot is happening in your pregnancy: An embryo’s cells start dividing to form organs, the embryo implants into the side of the uterus, the placenta must establish connections between your and your baby’s blood flow, and your immune system needs to get used to the new fetus inside of you. All of this means there are a lot of steps that can go wrong and result in a miscarriage.

Late miscarriages and much less common, occurring in 1 in 1,000 pregnancies, and happen between the end of the first trimester and week 20. They’re also more likely to be caused by exposure to toxins, placenta or cervix problems, or the mother’s health.

Types of miscarriage

There are a number of different types of miscarriage, depending on when it happens and the cause. A few of the most common include:

Chemical pregnancy. Many early miscarriages are known as a chemical pregnancy, which means that an egg was fertilized but never implanted in the uterus. Although a chemical pregnancy causes an increase in the pregnancy hormone hCG (and therefore a positive pregnancy test), an ultrasound would show no placenta or gestational sac.

Ectopic pregnancy. In an ectopic pregnancy, the embryo implants — but not in the right place (often a fallopian tube or the cervix instead of the uterus). The cramping and bleeding caused by an ectopic pregnancy are similar to the usual signs of a miscarriage, but they can lead to even more severe complications when the embryo ruptures, breaking off the area it incorrectly implanted into. To rule out an ectopic pregnancy, always get bleeding and cramping in early pregnancy checked out by a healthcare practitioner.

Molar pregnancy. When an egg that’s missing some of its parts — namely the genetic material — ends up fertilized by a sperm, it may start to grow into a mass in the uterus. While the cells never begin developing into a fetus, they can cause an increase in pregnancy hormones, making a woman think she’s pregnant for a short time, though these pregnancies always end in miscarriage.

Blighted ovum. A fertilized egg that attaches to the wall of the uterus and begins to develop a placenta (which produces hCG) before it stops growing is a blighted ovum, or an empty gestational sac that can be seen on an ultrasound.

Threatened miscarriage. If a health care practitioner suspects — at any point until 20 weeks — that heavy bleeding indicates a miscarriage is likely to occur, he may diagnose a threatened miscarriage. In this case, a miscarriage hasn’t actually yet occurred (a fetal heartbeat can even still be heard during an ultrasound). In fact, more than half of women with a threatened miscarriage go on to have a healthy, full-term pregnancy by following guidance from their health care practitioner, who may recommend rest or medication to help prevent a miscarriage.

Inevitable miscarriage. If a woman is bleeding heavily and a physical exam shows the cervix is open, a miscarriage is called “inevitable.” That means it’s already in the process of happening (the open cervix is how the body naturally expels tissue from the pregnancy), and unfortunately it can’t be stopped.

Missed miscarriage. Occasionally, women have a miscarriage without bleeding, known as a missed miscarriage. In these cases, you won’t know you’ve miscarried until your next prenatal appointment, when an ultrasound fails to find a fetal heartbeat.

In rare cases, miscarriages can be misdiagnosed. If you’re bleeding and your practitioner can’t find a fetal heartbeat (which can sometimes be tricky even in a healthy pregnancy), he might diagnose a miscarriage when an embryo is still thriving. If you stop bleeding, however, and continue to have pregnancy symptoms, a second ultrasound — where the heartbeat is hopefully heard — could confirm that your baby is still thriving.

What are the symptoms of a miscarriage?

The symptoms of a miscarriage can vary from woman to woman (and even be completely different if one woman experiences multiple miscarriages over time). But the most common signs include:

Cramping or pain in the lower back or abdomen

Heavy bleeding (possibly with clots or tissue) similar to a period

Lighter bleeding that lasts for more than three days

A disappearance of any pregnancy signs you were experiencing (such as nausea and breast tenderness)

Keep in mind, brief, light spotting is usually totally normal — and there’s no reason for immediate concern. But if you’re going through more than a pad an hour, or your bleeding has lasted more than three days, make sure to check in with your healthcare provider right away.

How is a miscarriage diagnosed?

If you’re experiencing any of the above symptoms, call your practitioner. He or she will evaluate the bleeding and then possibly measure your hCG (hormone) levels, check whether your cervix is open (it should be closed during pregnancy), perform an ultrasound to look for a healthy gestational sac and placenta, and listen for a fetal heartbeat. The results of these tests will help your healthcare provider determine whether you’ve miscarried.

If your cervix has started to dilate but you have no bleeding or pain, your practitioner may diagnose you with an incompetent cervix and perform cerclage (stitching the cervix closed) to prevent a late miscarriage.

If you have miscarried, chances are it was complete — or all the contents of the uterus (including not only a fetus, but the placenta and all the extra uterine lining) are expelled naturally, which can take up to two weeks. But sometimes, parts of the pregnancy (called “retained products of conception” by healthcare practitioners) remain in the uterus. For the body to recover and resume normal menstrual cycles, the uterus needs to be emptied. So, in some cases of incomplete miscarriages, healthcare providers will recommend pills or surgery to help your body clear out the uterus. You’ll also need to take some extra precautions after miscarriage, including avoiding inserting anything in the vagina for two weeks to prevent infection.

Risk factors

Even though miscarriages are common in every population of women around the globe, there are some factors that can boost your risk:

Age. Studies have found that older moms are more likely to have miscarriages — most likely because their eggs (and their partners' sperm) are more likely to have genetic defects. About one in three pregnancies after the age of 40 ends in miscarriage.

Vitamin levels . Researchers have found that deficiencies in vitamin D and vitamin B can increase a woman’s risk of miscarrying. Other vitamins — like vitamin A — have the opposite pattern: high levels can be dangerous during pregnancy. Taking a prenatal vitamin and getting your vitamin levels tested by your healthcare provider can help lessen these risks.

Untreated thyroid imbalances. Thyroid hormones affect the whole body and can alter levels of other hormones, including those that play a role in pregnancy. Both hypothyroidism and hyperthyroidism have been linked with miscarriage risks. Most health care providers test a woman’s thyroid levels throughout pregnancy, especially if she’s been diagnosed with thyroid problems in the past.

Being overweight or underweight. Obese women(those with a BMI of 30 or higher) have a significantly higher risk of miscarrying. Likewise, women with a BMI under 18 are more likely to miscarry.

Smoking or alcohol use. Both current and former smokers have an increased miscarriage risk compared with people who have never smoked. Studies have also shown that high levels of alcohol intake around the time of conception by both mom and dad can boost the chances of a miscarriage. If you’re pregnant or trying to get pregnant, it’s a great time to quit smoking and cut back on drinking alcohol.

Certain STDs. Sexually transmitted diseases, including syphillis and some forms of viral hepatitis, can make a woman more prone to having a miscarriage.

Large uterine fibroids. These benign tumors — which are extremely common in women as they age — can cause pregnancy complications including an increased miscarriage risk if they’re particularly large, in particular areas of the uterus, or if they start to grow in response to pregnancy hormones.

Chronic diseases. Pregnant women with kidney disease, autoimmune diseases, polycystic ovarian syndrome (PCOS) and diabetes are at higher than usual risk of miscarrying. If you have one of these conditions, your pregnancy may be classified as high-risk and you’ll have more appointments and monitoring than other women to help manage your disease and keep your growing baby safe.

Medications. Doctors recommend that pregnant women avoid a number of over-the-counter medications including common painkillers during pregnancy. Many of these cause birth defects, but some also have been linked to miscarriages.

Environmental toxins. Exposure to lead, mercury, organic solvents and ionizing radiation has been found to increase the risk of miscarrying. These toxins likely aren’t found in your home but are sometimes present in the workplaces of farming or industrial manufacturing facilities. Although the levels required to affect pregnancy would most likely cause you to experience adverse noticeable side effects as well, if you’re concerned about your exponsure talk to your doctor.

Spacing between pregnancies. Getting pregnant again less than six months after your last full-term pregnancy might boost your miscarriage risk just a little bit — although the evidence is mixed. Since this short spacing between pregnancies can lead to other complications including preterm birth, it’s best to give your uterus a longer time to recover.

Keep in mind, of course, that most of these risk factors lead to only very slight increases in miscarriage risk — a single glass of wine before you know you’re pregnant, or missing your vitamins for a few days is not something to be concerned about. And many women with none of these risk factors still have miscarriages. Remember, too, that lots of rumored risk factors aren’t really linked to your chances of having a miscarriage at all. (If your mom had a miscarriage or two, that doesn’t make you more likely to have one as well, for example.)

Preventing miscarriage

Most miscarriages can’t be prevented. So unless your healthcare provider has diagnosed a specific risk factor — such as a thyroid imbalance or blood clotting disorder — he will generally recommend simply leading a healthy lifestyle, which includes:

Taking a prenatal vitamin that includes folic acid and other B vitamins; research has shown that some women have trouble conceiving and/or sustaining a pregnancy because of a folic acid or vitamin B12 deficiency that can be treated with appropriate supplementation

Taking steps to avoid and treat infections such as STDs

Staying away from cigarettes and alcohol

Take only medications that get the OK from your practitioner

What if I’ve had more than one miscarriage?

If you’ve had two or three miscarriages, your healthcare practitioner will probably run extensive tests to see if he can find a cause. Around half the time, he won’t be able to find a single reason you’ve had multiple miscarriages. But sometimes he may discover an untreated health problem, such as an autoimmune disease (where the mother’s immune system attacks the embryo), thyroid problem, misshapen uterus or one of a few very rare disorders that can make your body reject pregnancies. You and your partner may be tested, too, for blood-clotting disorders (some women produce antibodies that attack their own tissues, causing blood clots that can clog the maternal blood vessels that feed the placenta). An ultrasound, MRI or CT scan may be performed on your uterus, your uterine cavity may be assessed with hysteroscopy, and the miscarried fetus itself can be tested for chromosomal abnormalities. If he does pinpoint one of these causes, he’ll be able to help reduce your chances of future miscarriages with treatments, including surgery to correct cervical or uterine issues and medications to manage hormonal imbalances.

The good news: Most women who’ve had a miscarriage (even more than one) eventually go on to have a healthy pregnancy, although you may need to manage future pregnancies differently. According to the American Congress of Obstetrics and Gynecology, even after four consecutive losses around 65 percent of women go on to carry their next pregnancy to term.

Whether it’s your first or fifth, in the aftermath of a miscarriage it’s important to take care of both your body and mind. After a miscarriage, check in with your healthcare provider and allow yourself time to grieve. Then when you’re ready, find someone to talk to (whether it’s a support group or a friend who’s been through the same thing). Sharing your feelings openly with your partner may help too. Remember: You’re in this together.

The material on this website is provided for educational purposes only and is not to be used for medical advice, diagnosis, or treatment, or in place of therapy or medical care. Use of this site is subject to our terms of use and privacy policy

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